The present invention relates to a process system and apparatus for treating contaminated liquid to remove volatile organic compounds (VOCs) and other objectionable contaminants from said contaminated liquid, such as contaminated groundwater, surface water, or process water.
Groundwater contamination has been frequently caused by chemical spills, run-off of agricultural herbicides and pesticides, and leakage from sanitary landfills, surface impondments, or underground storage tanks (UST). Groundwater treatment for decontamination becomes an urgent task because half the U.S. population depends on groundwater for their drinking water supply. By the year 2000, the nation's total groundwater demand will double.
Another half the U.S. population depends on surface water (lake water, reservoir water, river water, etc.) of which 50 percent has been protected by communities as their source of drinking water supply, and the remaining 50 percent has been severely polluted by industrial effluents, septic tank effluents and accidental chemical spills. There has been an increasing trend for the nation's population. The higher the population, the higher the water demand. The polluted surface water should be purified not only for environmental conservation, but also for developing more available drinking water sources in the future.
Various industrial process waters containing harmful or even hazardous substances must be properly pretreated for resource recovery or pollution load reduction before being discharged to municipal sewers or receiving waters.
Many conventional unit processes, such as chemical coagulation, flocculation, oxidation, sedimentation clarification, flotation clarification, air stripping tower, granular activated carbon filtration, sand filtration, ozonation, ultra violet (UV) light treatment, chlorination, reverse osmosis (RO), ultrafiltration, microfiltration, ion exchange, distillation, etc. are now available for water purification. Each unit process can only partially purify a contaminated water. In general a feasible water treatment system involving the use of several unit processes is required to accomplish the government required water quality goal, and such a feasible water treatment system is custom designed by a consulting engineer and is usually expensive.
A typical water treatment system being seriously considered by the engineers for groundwater decontamination in New Jersey at a liquid flow rate of 150 gallons per minute includes a pretreatment unit, two air stripping units, a liquid phase granular activated carbon (GAC) polishing filter, and a storage disinfection holding tank. Besides, a gas phase GAC filter with an air flow capacity of 1100 standard cubic foot per minute is required for air emission control. The contractor quoted price in 1989 including equipment, piping, design and installation approached U.S. $500,000, which was only affordable by a government agency. In addition to the high cost, there are possibilities to have secondary air pollution and secondary water pollution. The effluent from the gas phase GAC filter is subject to air emission monitoring in order to comply with very stringent air quality standards, while the wastewaters from the pretreatment unit and the liquid phase GAC filter are subject to wastewater monitoring in order to comply with stringent water quality standards. The long-time operation, maintenance, monitoring and reporting for a typical groundwater decontamination project are very costly, and the engineers decide not to continue the project if their system can not decontaminate the groundwater within 5 months.
To save about 2/3 of costs in equipment, design, and installation of a water treatment system and to totally eliminate secondary air pollution and secondary water pollution for possible wide adoption by industry, communities, or individual property owners, the conventional water treatment technologies must be optimized and packaged. Optimizing and packaging feasible unit processes to form a system or apparatus for more efficient and more cost-effective treatment of any contaminated water are the primary objectives of the present invention. The secondary objective of the present invention is to eliminate secondary air pollution and secondary water pollution.